Heretofore adhesives used to attach sheets of roofing membranes to each other have been made from various components. U.S. Pat. No. 4,851,462 describes an adhesive made from a halogenated butyl rubber crosslinked during polymerization with divinyl benzene, a high softening point thermoplastic resin and a solvent. U.S. Pat. No. 4,603,164 describes an adhesive made from halogenated butyl rubber, butyl rubber crosslinked during polymerization with 1,4 divinyl benzene or similar unsaturated crosslinking compounds, a high softening point hydrocarbon resin, optional ethylene-propylene-non-conjugated diene terpolymer and aliphatic polyisocyanate.
U.S. Pat. No. 4,501,842 describes an adhesive made from halogenated butyl rubber, pre-crosslinked butyl rubber made by incorporating a crosslinking agent during polymerization of the butyl rubber, styrene/ethylene butylene/styrene block thermoplastic rubber, a thermoplastic petroleum based hydrocarbon feedstock derived aliphatic monomer resin, and an aliphatic isocyanate. U.S. Pat. No. 4,881,996 relates to a butyl splice adhesive made of halogenated pre-crosslinked isobutylene-isoprene copolymer butyl rubber, thermoplastic copolymer, hydrocarbon resin, quinoid cure mixture and solvent.
The installers of EPDM rubber membrane roofs require that the roofing adhesives have a number of rigorous physical characteristics which facilitate their application and durability. These include useful application viscosity, low Weissenberg values (Weissenberg values are a measure of brushability and flowability; the lower the number for an adhesive, the more easily it will apply), peel performance at one hour of at least one pound per linear inch (pli) and strength of 24 hours or more after passing the Dead Weight Shear Test (DWST) at 158.degree. F. (70.degree. C.) in an ambient humidity oven. DWST is meant to simulate summer conditions on a hot roof. When the adhesive passes such stringent tests it can be efficiently applied and will not fail during the crucial early moments while workers are still walking on the bonded membranes or large fluctuations in temperature occur.
The adhesives previously developed often fail these rigorous tests and sometimes even form unusable gels in their containers before they can be used. It would certainly be desirable to develop an adhesive which would pass these tests consistently and be storage stable as well.